A circuit switched network usually includes multiple switch nodes which are arranged in a topology referred to in the art as a “shared mesh network”. Within the shared mesh network, user traffic can be transported between any two locations using predefined connections specifying a working path including particular links and/or switch nodes for conveying the user traffic.
The switch nodes are provided with a control module. The control modules of the switch nodes function together to aid in the control and management of the circuit switched networks. The control modules can run a variety of protocols for conducting the control and management of the circuit switched networks. One prominent protocol is referred to in the art as “Generalized Multiprotocol Label Switching (GMPLS).
Generalized Multiprotocol Label Switching (GMPLS) includes multiple types of optical channel data unit label switched paths including protection and recovery mechanisms which specifies predefined (1) working connections (or paths) within a shared mesh network having multiple nodes and communication links for transmitting data between a headend node and a tailend node; and (2) protecting connections (or paths) specifying a different group of nodes and/or communication links for transmitting data between the headend node to the tailend node in the event that one or more of the working paths fail. A first node of a working path and/or a protecting path is referred to as a headend node. A last node of a working path and/or a protecting path is referred to as a tailend node. Data is initially transmitted over the optical channel data unit label switched path, referred to as the working path, and then, when a working path fails, the headend node or tailend node activates one of the protecting paths for redirecting data within the shared mesh network.
Shared Mesh Protection (SMP) is a common protection and recovery mechanism in transport networks, where multiple paths can share the same set of network resources for protection purposes.
An exemplary mesh network 100 is shown in FIG. 1, by way of example. In FIG. 1, the mesh network 100 includes switch nodes 102 (hereinafter referred to as “nodes” 102) and labeled as A, B, C, D, E, F, G, H, I, J and K. Some of the nodes 102 are denoted as a headend node 104 or tailend node 106 for a particular path in accordance to the path setup direction. Other nodes 102 are known as intermediate nodes 108. In this example, the mesh network 100 includes headend nodes 104-A and 104-K; tailend nodes 106-D and 106-H; and intermediate nodes 108-B, 108-C, 108-E, 108-F, 108-G, 108-I, and 108-J. The mesh network 100 in FIG. 1 also includes two working paths 110a and 110b; and two protecting paths 112a and 112b. Thus, the working paths 110a and 110b are formed by the nodes {104-A, 108-B, 108-C, 106-D}, and {104-K, 108-J, 108-I, 106-H} respectively; and the protecting paths 112a and 112b are formed by the nodes {104-A, 108-E, 108-F, 108-G, 106-D}, and {104-K, 108-G, 108-F, 108-E, 106-H} respectively. Connections are established via control planes prior to a failure of the mesh network 100. The switch nodes A-K are coupled by communication links 114a-k, which can be fiber optic cables, electronics cables, wireless communication links, or the like.
In this example, the communication links 114f and 114e between intermediate nodes 108-E, 108-F and 108-G are shared by both protecting paths 112a and 112b. The working paths 110 and the protecting paths 112 can be established by the nodes A-K using GMPLS protocols prior to any network failure. The working paths 110 and the protecting paths 112 may be bi-directional or co-routed, for example.
In Shared Mesh Protection, initially operators set up both working paths 110 and protecting paths 112. During setup, operators specify the network resources, for example, switch nodes A-K, communication links 114, and timeslots, for each path. The operators will activate the working paths 110 with the appropriate resources on the intermediate nodes 108; however, the protecting paths 112 will be reserved but the resources on the intermediate nodes 108 will not be initially activated. Depending on network planning requirements, such as Shared Risk Link Group (SRLG, including two or more links such as the communication links 114), protecting paths 112 may share the same set of resources on intermediate nodes 108-E, 108-F, and 108-G. The resource assignment is a part of the control-plane Connection Admission Control (CAC) operation taking place on each node.
Upon detection of working path 110 failure (for example, if the communication link 114b between intermediate nodes 108-B and 108-C is cut), the edgenode (headend node 104-A and/or tailend node 106-D) will transmit the activation messages to activate the protecting path 112a. By processing the activation messages, the intermediate nodes (108-E, 108-F, and 108-G) will program the switch fabric and configure the appropriate resources. Upon the completion of the activation, the edgenode (for example, headend node 104-A) will switch the user traffic to the protecting path 112.
In general, logical tables in one or more databases may be used to support protecting path 112 activation logic. Preferably, the tables include one or more connection tables, one or more logical timeslot tables, and one or more real timeslot tables. The connection table(s) maintains the connection-related information, including label, interfaces, and associated timeslot information for the connections. The logical timeslot table(s) is a timeslot translation table(s) between connections and timeslots. The real timeslot table(s) maintains the timeslot-related information, including the active connections that are currently conveying traffic and reserved connections for all timeslots. A reserved connection means there is not any active traffic on the timeslot. In the situation where a protecting path 112 is identified in the connection table, the protecting path's associated timeslots can be readily discovered utilizing the logic timeslot table and the real timeslot table. A common conflict matrix has been shared by the nodes 102 in the network 100, and may be used to avoid dropped or rejected connections due to insufficient bandwidth. However, the common conflict matrix did not indicate which SRLGs share bandwidth in the conflict matrix.
The protecting paths 112 play an important role in Shared Mesh Protection. However, there is no standard method in detecting which particular SRLGs are consuming resources on each communication link 114. Without having this information, the protecting connection setup could be directed via a link that may not have sufficient bandwidth to handle the traffic, and may reject the connection. This causes a protecting path 112 failure, and the intermediate node 108 may reject the connection, which forces the node upstream of the intermediate node 108 to set up a new protecting path 112. This is commonly known as “crankback” in network operation, and it causes significant delays in configuring shared mesh protection connections.